This invention relates in general to xerographic reproducing apparatus and more particularly to a contact fuser and temperature sensing device therefor.
In the process of Xerography, latent electrostatic images are formed on a support member, for example, plain paper, with the subsequent rendering of the latent images visible by the application of electroscopic marking particles, commonly referred to as toner. The toner images can be fixed directly upon the support member on which they are formed or they can be transferred to another support member with subsequent fixing of the images thereto.
Fixing of toner images can be accomplished by various methods one of which is by the employment of thermal energy. In order to permanently fix or fuse toner images onto a support member by means of thermal energy it is necessary to elevate the temperature of the toner material to a point at which the constituents of the toner coalesce and become tacky. This action causes the toner to be absorbed to some extent into the fibers of the paper. Thereafter as the toner cools, solidification of the toner material occurs causing it to be firmly bonded to the support member. In the process of Xerography, the use of thermal energy for fixing toner images is old and well known.
One approach to thermal fixing or fusing of toner images onto a support member is to pass the support member between a pair of fuser roll members one roll of which is heated. The support member is passed through the nip formed by the fusing roll members with the toner images contacting the heated roll. In order to elevate the temperature of the toner material for proper fusing it is necessary to control the surface temperature of the heated roll member.
A common means of controlling the temperature of the heated fuser roll member is to provide a contact temperature sensing device which frictionally engages the surface of the heated fuser roll member. In order to accurately control the fuser roll temperature with a contact sensing device it is necessary to insure that the sensing element is properly positioned relative to the surface of the fuser roll.
Accordingly, the primary object of this invention is to provide a new and improved fuser apparatus for a xerographic reproducing machine.
Another object of this invention is to provide a new and improved temperature sensing device for use in conjunction with a contact fuser apparatus utilized in a xerographic reproducing machine.
Yet another object of this invention is to provide a temperature sensing device having a thermally conductive cap member containing temperature sensing elements which cap member is constructed in a manner to insure proper positioning of the temperature sensing device relative to the surface whose temperature is to be controlled.